Current Components and Their Temperature Dependence of Green and Blue Light-Emitting Diodes: A Quantitative Comparison

• Published in: IEEE transactions on electron devices Vol. 61; no. 4; pp. 1101 - 1108
• Main Authors: Kim, Da-Woon, Lee, Young-Chan, Ryu, Jong-Ok, Kim, Sang-Bae
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Current measurement; Current-voltage (I{-}V) characteristics; Efficiency; green gap; Green products; Light emitting diodes; light-emitting diodes (LEDs); quantum efficiency; Radiative recombination; Temperature dependence; Temperature measurement; Temperature sensors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2014.2305439

We have quantitatively compared the portion and temperature dependence of each current component in commercial green and blue light-emitting diodes (LEDs) using a current-component analysis method for the purpose of finding out the origin of the green-gap problem, which is a major roadblock to the next-generation solid-state lighting. The analysis results show that the loss current, which is the origin of the efficiency droop, decreases the internal quantum efficiency of the green LED significantly and is the primary origin of the green-gap problem. In addition, the loss current I loss and the radiation current I rad that actually generates light output are approximately related as I loss ∝ I rad 1.5 almost independent of the temperature. Therefore, I loss and I rad 1.5 have the similar temperature dependence in both the green and blue LEDs, and the loss current is approximately proportional to the cube of the carrier concentration. The temperature and the carrier-concentration dependences are valuable clues to the physical origin of the green-gap problem and the efficiency droop. On the other hand, the portion and the temperature sensitivity of the Shockley-Read-Hall (SRH) nonradiative recombination current are similar in the green and blue LEDs. Therefore, in our samples, the SRH nonradiative recombination is not the origin of the green-gap problem.